Follow comments and refine the python wrapper of reshape_op

python/paddle/fluid/layers/nn.py

@@ -3361,7 +3361,9 @@ def reshape(x, shape, act=None, inplace=True, name=None):
 
     Examples:
         .. code-block:: python
-            data = fluid.layers.data(name='data', shape=[2, 4, 6], dtype='float32')
+            data = fluid.layers.data(
+                name='data', shape=[2, 4, 6], dtype='float32'
+            )
             reshaped = fluid.layers.reshape(
                 x=data, shape=[-1, 0, 3, 2], act='tanh', inplace=True
             )
@@ -3371,6 +3373,21 @@ def reshape(x, shape, act=None, inplace=True, name=None):
     if not (isinstance(shape, list) or isinstance(shape, tuple)):
         raise ValueError("Input shape must be a python lsit or tuple.")
 
+    # Validate the shape
+    unk_dim_idx = -1
+    for dim_idx, dim_size in enumerate(shape):
+        if dim_size == -1:
+            assert unk_dim_idx == -1, (
+                "Only one dimension in shape can be unknown.")
+            unk_dim_idx = dim_idx
+        elif dim_size == 0:
+            assert dim_idx < len(x.shape), (
+                "The indice of 0s in shape can not exceed Rank(X).")
+        else:
+            assert dim_size > 0, (
+                "Each dimension size given in shape must not be negtive "
+                "except one unknown dimension.")
+
     helper = LayerHelper("reshape", **locals())
     reshaped = helper.create_tmp_variable(dtype=x.dtype)
     helper.append_op(